1. Field of the Disclosure
The present disclosure relates to an input device that is used to input information in an information apparatus, such as a computer or a smart phone, and more particularly, to an input device that specifies a region of an operation surface which an object, such as a finger or a pen, approaches and inputs information on the basis of the specified region.
2. Description of the Related Art
Devices, such as touch pads or touch panels including sensors, which detect the contact position of an object such as a finger or a pen, have been widely spread as input interfaces of information apparatuses including notebook PCs, tablet terminals, and smart phones. There are various types of sensors, which detect the contact position of the object, such as a resistance-film-type sensor and a capacitance-type sensor. In recent years, a capacitance-type sensor, which can respond to a “multi-touch method” for detecting a plurality of contact positions, has come into widespread use.
In a general capacitance-type sensor including a plurality of electrodes, which are arranged in a lattice shape, the capacitance (mutual capacitance) between the electrodes or the capacitance (self-capacitance) between the electrode and the ground is detected. A capacitance-type touch sensor disclosed in Japanese Unexamined Patent Application Publication No. 2012-198607 includes a plurality of X electrodes that are arranged in the X direction and a plurality of Y electrodes that are arranged in the Y direction (FIG. 1). When an operation body, such as a finger, approaches the X electrode (Y electrode), electrostatic coupling between the operation body and the X electrode (Y electrode) is formed and the capacitance of the X electrode (Y electrode) increases. The capacitances of each X electrode and each Y electrode are monitored to detect the approach position of the operation body.
In the input device disclosed in Japanese Unexamined Patent Application Publication No. 2012-198607, a moving average process is performed on the basis of target coordinates and a predetermined number of coordinates acquired before and after the target coordinates and the average value is set to correction coordinates to remove noise. When this noise removal process is performed, for example, the wobble of the coordinates is suppressed even in a high noise environment and an operation error is less likely to occur. However, when the noise removal process, such as the moving average process, is performed for the output signal from the sensor, high-frequency components are attenuated. As a result, a response to the input of the sensor is delayed. In the input device disclosed in Japanese Unexamined Patent Application Publication No. 2012-198607, the same noise removal process as that in a high noise environment is performed in a low noise environment. Therefore, a large delay occurs due to the noise removal process.